Porphyrins are derivatives of porphine, a conjugated cyclic structure of four pyrrole rings linked through their 2- and 5-positions by methine bridges. Porphyrins can be covalently attached to other molecules. The electronic features of the porphyrin ring system can be altered by the attachment of one or more substituents. The term "porphyrin" includes derivatives wherein a metal atom is inserted into the ring system, as well as molecular systems in which ligands are attached to the metal. The substituents, as well as the overall porphyrin structure, can be neutral, positively charged, or negatively charged.
Electron-deficient porphyrins (i.e., porphyrins bearing substituents that are electron-withdrawing relative to hydrogen) have been suggested for use as industrial oxidation and reduction catalysts. Strapped porphyrins, wherein atoms at or near the periphery of the porphyrin ring system are covalently bound through linkages (straps) that do not include the porphyrin core, also have been suggested for a variety of uses, including use as enantioselective oxidation catalysts. A number electron-deficient porphyrins and strapped porphyrins have been prepared, but many known synthetic methods generally proceed in low yield, if at all, and cannot be used to produce many types of porphyrins.
Accordingly, there exists a need in the art for efficient synthetic methods capable of producing a greater variety of electron-deficient and/or strapped porphyrins.